And when the Girls star Jemima Kirke flashed some serious axillary growth on the red carpet last week, it was officially a trend. Search for #pithairdontcare on Instagram and you will see hundreds of women of all ages, races, shapes and styles, proudly flaunting their hair "up there".

So when I wrote in Grazia magazine last week about growing out my own armpit hair, I was surprised by how divisive going au naturel is, even in 2015. I stopped shaving under my arms about 18 months ago (partly through laziness, curiosity and, y'know, winter) and discovered that I liked how it felt (less itchy and stubbly) and how it looked (carefree, cool, a bit Betty Blue slash Sophia Loren).

On Twitter a lot of people were enthusiastic about "equal rights for hair" and told me I was their "pit-spiration"; others found it "repulsive" or simply "ewwww".

Friends and colleagues have told me I'm "brave" (er, thanks) and asked if they can have a peek. (If I'm wearing a sleeveless top, sure. If not, this could be awkward for everyone.)

A lot of women tweeted me to describe themselves as "hairless feminists" who were "bald and proud". Social conditioning is a powerful thing.

One blogger asked me: "If having hairy armpits is a feminist statement, how about you stop using deodorant, having manicures, wearing make-up and writing for a women's fashion magazine too?" It's an interesting point, and the fact that a photo of my furry pits appeared in the same pages as adverts for a Veet spa wax and Bic lady razors hasn't passed me by. But, if anything, I think it makes it even more relevant.

Although the ancient Egyptians apparently created their own Immac out of beeswax, before the First World War no woman shaved her legs (or anything else, for that matter).

As fashion became more revealing, Gillette's first razor for women came out in 1915, specifically marketed as the "safest and most sanitary method of acquiring a smooth underarm", and hair-free pits soon became the norm. By the late 1960s, having armpit hair was a political statement and Patti Smith casually displayed hers on the cover of her 1978 album, Easter. But, up until very recently - bar Julia Roberts's memorable pit-flashing film premiere in 1999 - smooth armpits have been de rigueur.

I'd never say that being a feminist and deciding to depilate are mutually exclusive. But are women really choosing to remove underarm hair for themselves? Or have we all just swallowed the image of conventional, hairless beauty pushed on us by a multimillion-pound industry? If feminism is, to a large extent, just about gender equality, how is it right for one sex to spend time, money, effort and pain removing their body hair just to feel normal?

Anyone doubting the power of the pit should note that feminist activists in China are currently holding an "armpit hair contest", encouraging women to share their hairy underarms on the blogging site Weibo. The competition, organised by the women's-rights advocate Xiao Meili, concludes on Thursday and has had more than one million page views, as well as submissions from prominent feminists such as Wei Tingting, Li Tingting and Zheng Shuran - three of the activists who were detained in March before a planned protest against sexual harassment on public transport.

"I'm not calling on everybody to grow underarm hair," Xiao said. "I'm just saying, if some people don't want to shave, the rest of us should not think their underarm hair is disgusting, unhygienic, uncivil, or not feminine enough."